Infections of the Digestive Tract and E. Coli

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  • Created by: Rose
  • Created on: 20-05-14 18:16
Define diarrhoea
Change in frequency/consistency of stools
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Define dysentry
Diarrhoea associated with abdominal pain and mucus/blood in stools
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What is the general term given relating to diarrhoea/dysentry?
Gastroenteritis
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The agent is usually aquired..?
Exogenously
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Name 4 common causes of diarrhoea
E. coli, Salmonella, Shigella, Campylobacter, Clostridium
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* E. Coli *
* E. Coli *
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Is E. coli gram + or -?
Gram - bacilli
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How are the flagella organised on E. coli?
Peritrichous (all over surface)
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What agar does E. coli grow on?
MacConkey agar
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What colour colonies do E. coli form on MacConkey agar, and why?
Red, because they are lactose fermenting
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Which type of bacteria can not grow on MacConkey agar?
Gram + bacteria (e.g. S. aureus will NOT grow)
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E. Coli Antigens
E. Coli Antigens
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E. coli has a somatic __ antigen which is part of the _____
O; Cell Wall
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E. coli has a flagellar __ antigen
E. coli has a flagellar __ antigen
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Is the somatic or flagellar antigen more species specific?
Flagellar
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The STRAIN is made up of the O and H type of the pathogen
The STRAIN is made up of the O and H type of the pathogen
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Which two infections does E. coli commonly cause?
Diarrhoea (gastroenteritis), UTI
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* Pathotypes causing diarrhoea *
* Pathotypes causing diarrhoea *
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What does ETEC stand for?
Enterotoxigenic E. coli
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What does STEC stand for?
Shiga-Toxin Producing E. coli
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What does EPEC stand for?
Enteropathogenic E. coli
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What does EAEC stand for?
Enteroaggregative E. coli
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* ETEC *
* ETEC *
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ETEC commonly causes...?
Traveller's Diarrhoea
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How does ETEC cause diarrhoea?
Adheres to GI epithelia via CFAs, produces STABLE and LABILE toxins affecting cAMP and cGMP production, increasing fluid in GI = diarrhea.
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EPEC is common in who?
Children under 2yrs
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The two stages of EPEC attachment are?
Initial attachment (pilus), Intimate attachment (effacing lesion)
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There is loss of what at the site of intimate attachment?
Microvilli
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The intimate attachment is due to what?
Type III secretion system
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The type III secretion system is encoded by what?
A pathogenicity island called LEE
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LEE encodes the type III secretion system
LEE encodes the type III secretion system
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What is the type III secretion system?
Needle-like structure on surface of EPEC
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How does the type III secretion system work?
Insert needle into host cell, inject Tir protein into host
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What does the Tir protein do?
Binds intimin on bacterial cell, bringing epithelial cell and bacteria close together
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What does EHEC stand for?
Enterohaemorrhagic E. coli
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EHEC / STEC / VTEC are the SAME THING
EHEC / STEC / VTEC are the SAME THING
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Which toxin does EHEC produce?
Shiga toxin
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What is STEC linked to?
Hemolytic uremic syndrome
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* What is the most common serotype for EHEC?! *
O157 : H7
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What is the common reservoir for EHEC?
Cattle
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How do humans acquire the infection?
Infected meat or vegetables
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How does EHEC adhere?
Similar to EPEC : Type III system
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How is the shiga toxin released?
Phage mediated lysis (EHEC lacks secretory mechanism for Shiga toxin)
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HENCE ANTIBIOTICS ARE DISCOURAGED IN EHEC INFECTION
HENCE ANTIBIOTICS ARE DISCOURAGED IN EHEC INFECTION
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How does the Shiga toxin work?
Enters circulation, lyses RBCs and inhibits protein synthesis, damage to kidneys
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Which serotype caused the 2011 German outbreak of STEC?
O104 : H4
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The bacteria causing the outbreak was not EHEC BUT?
EAEC (EAggEC)
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EAggEC are associated with a different binding mechanism to other pathotypes. How so?
Stacked brick adherence mechanism
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The German outbreak EAggEC was capable of producing Shiga toxin... thus acquired gene
The German outbreak EAggEC was capable of producing Shiga toxin... thus acquired gene
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What was unusual about the strain O104 : H4? (2 things)
1. Disproportionate number of related HUS cases. 2. Very resistant to antibiotics
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Why are antibiotics not given for diarrhoea?
If it is EHEC, Shiga toxin will be released if cells lysed and thus can cause hemolytic uremic syndrome
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Which agar is used to identify O157 : H7?
Sorbitol MacConkey Agar (SMAC)
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What colour do O157 : H7 appear on SMAC and why?
Pale in colour as they are non fermenters (normal flora E. coli ARE fermenters and will thus be pink in colour)
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Which two methods can we use to distinguish O157 : H7 from other E. coli?
PCR check for Shiga toxin gene, and serology confirming O and H type. PCR better.
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Which gene produces the Shiga toxin?
Stx gene
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Other cards in this set

Card 2

Front

Define dysentry

Back

Diarrhoea associated with abdominal pain and mucus/blood in stools

Card 3

Front

What is the general term given relating to diarrhoea/dysentry?

Back

Preview of the front of card 3

Card 4

Front

The agent is usually aquired..?

Back

Preview of the front of card 4

Card 5

Front

Name 4 common causes of diarrhoea

Back

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